1. Field of the Invention:
This invention relates to packing material units for use in liquid-gas contact apparatuses.
2. Description of the Prior Art:
It has been the general practice to employ packing units of a synthetic polymeric material as packing material for washing towers, absorption towers or distilling towers because of its superior corrosion resistance and low prices. Examples of such packing material units include a filamentous packing unit disclosed in U.S. Pat. No. 2,867,425 as shown in FIG. 6 of the accompanying drawing (hereinafter referred to as "unit A") and a similar filamentous packing unit disclosed in U.S. Pat. No. 3,752,453 as shown in FIG. 7 (hereinafter referred to as "unit B").
In designing the packing material for the mass transfer process between liquid and gas phases, the following properties are usually taken into consideration as general criteria.
(1) Large surface area per unit volume;
(2) Large free volume permitting, with a minimized resistance, the passage of liquid and gas flows through the tower;
(3) High mechanical strength;
(4) Small amount of resin per unit volume; and
(5) Feasibility of injection molding.
The above-mentioned packing units A and B almost satisfy these requirements. From an economical point of view, however, it is still desired to reduce the number of packing units required to fill a unit volume, which is as large as 32,500/m.sup.3 in the case of unit A and 25,000/m.sup.3 in the case of unit B. Less packing units are required per unit packed space in the case of the unit B since it is provided with an outer ring which serves to reduce the amount of interlocking with adjacent units.
The reduction in the number of the packing units, however, normally leads to a reduction in surface area per unit volume, bringing about an undesired reduction in the interfacial area per unit contactor volume which is an important factor in the mass transfer between liquid and gas phases. Moreover, providing a further interlock-preventing member to reduce the number of packing units per unit packed space causes an increase in amount of the synthetic polymeric material and, if the thickness of the filaments is reduced to avoid this problem, the resulting packing units are then lowered in strength. Thus, the reduction of the filling number, i.e. the increase of the bulk volume, which is desirable from an economic point of view, has not been sought for in view of the impairment of other properties.